An assembly of nuclear fuel used in a nuclear power plant or the like is referred to as “fuel assembly”. A fuel assembly loaded in a nuclear reactor, burned for a predetermined period, and taken out from the nuclear reactor contains fission products (FP). Therefore, the fuel assembly is normally cooled in a cooling pit of a nuclear power plant or the like for a predetermined period. Thereafter, the fuel assembly is housed in a fuel assembly housing container having a radiation shielding function, transported to processing facilities or interim storage facilities by a vehicle or a ship, and stored at the facilities until reprocessing is performed. Patent Literature 1 discloses a buffer member positioned in a radial direction gap between a radioactive material assembly and a basket, and a spacer positioned in an axial direction gap between the radioactive material assembly and a lid.